Engines may use various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder. One type of fuel delivery uses a port injector for each cylinder to deliver fuel to respective cylinders. Still another type of fuel delivery uses a direct injector for each cylinder.
Engines have also been described using more than one injector to provide fuel to a single cylinder in an attempt to improve engine performance. Specifically, in US 2005/0155578 an engine is described using a port fuel injector and a direct injector in each cylinder of the engine.
Another approach utilizing multiple injection locations for different fuel types is described in the papers titled “Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection” and “Direct Injection Ethanol Boosted Gasoline Engine Biofuel Leveraging for Cost Effective Reduction of Oil Dependence and CO2 Emissions” by Heywood et al. Specifically, the Heywood et al. papers describe directly injecting ethanol to improve charge cooling effects, while relying on port injected gasoline for providing the majority of combusted fuel over a drive cycle.
However, the inventors herein have recognized several issues with such systems. For example, warmed-up engine operation may be optimized for various speed or load ranges by using multiple injectors per cylinder to each inject a portion of total fuel to give improved operation. However, when such speeds or loads are encountered during engine starting or warm-up, degraded operation may result due to effects on fuel injection and combustion caused by engine run-up, cold cylinder or valve temperatures, and other factors.
Thus, in one approach, a system is provided for an engine, comprising: a cylinder of the engine; a first injector configured to inject a first substance for said cylinder; a second injector configured to inject a second substance for said cylinder; a controller configured to commence combustion in the engine by injecting fuel for said cylinder, where said fuel is injected by only one of said first and second injectors during said start and warm-up.
In this way, it is possible to reduce the effects of degraded engine starting and warm-up under various operating conditions by using the injector most suited to the specific conditions of the start and warm-up, such as reduced engine temperature, reduced air temperature, or reduced barometric pressure.
In another approach, a system for an engine is provided, comprising: a cylinder of the engine; an injector configured to inject a mixture of gasoline and an alcohol for said cylinder; and a controller configured to vary a relative amount of said gasoline and alcohol to increase an amount of gasoline combusted in the engine during engine starting and warm-up. In this way, it is possible to provide improved engine starting and warm-up by preferentially using gasoline, at least under some conditions, to compensate for reduced engine temperature and other factors.